The present invention relates generally to operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a method of controlling a hydraulically actuated subsurface well tool.
Safety valves are being installed at progressively greater depths in wells. These increasing safety valve depths have created numerous problems for those responsible for the valve installations and operations.
One of these problems has to do with the need to run a control line to a safety valve installed at a very deep location in a well. An increase in the length of a control line brings with it the increased probability that a failure will be experienced in the control line at some point in the productive life of the well. This is due to, for example, an increased number of connections in the control line, an increased number of control line tubing sections, an increased probability of damage during installation, etc.
Various solutions have been proposed for dealing with this problem. Unfortunately, however, these prior solutions have required installation of an inordinate amount of additional equipment at the well, undue complexity and/or an increased probability of experiencing a failure requiring replacement of the safety valve, with the associated expense of killing the well, pulling the production string and installing a new production string.
What is needed is a method of controlling a hydraulically actuated subsurface well tool which does not require a large investment in additional equipment, which is relatively simple in construction and use, and which provides true redundancy for control lines installed in a well.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a method is provided which solves the above problems in the art.
In one aspect of the present invention, a method of controlling a subsurface hydraulically actuated well tool is provided. The method includes the steps of hydraulically connecting a first control line to a first piston of the well tool and hydraulically connecting a second control line to a second piston of the well tool. The well tool is operable in response to pressure in the first control line, and the well tool is operable in response to pressure in the second control line. The well tool is operated by applying pressure to both of the first and second control lines, and then, in response to failure of the first control line, the well tool is operated by applying pressure only to the second control line.
In another aspect of the present invention, a single pump is used to operate the well tool when applying pressure to both of the first and second control lines. The same pump is then used when operating the well tool by applying pressure to only the second control line.
In yet another aspect of the present invention, a method of controlling a surface controlled subsurface safety valve is provided. The safety valve includes first and second pistons operatively connected to an opening mechanism of the safety valve. The first and second pistons are hydraulically isolated from each other in the safety valve.
The safety valve is operated by applying pressure to both of first and second control lines hydraulically connected to the first and second pistons, respectively. Then the safety valve is operated by applying pressure to only the second control line.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings.